1. Field of the Invention
Numerous deposit-forming substances are inherent in hydrocarbon fuels. These substances when used in internal combustion engines tend to form deposits on and around constricted areas of the engine contacted by the fuel. Typical areas commonly and sometimes seriously burdened by the formation of deposits include carburetor ports, the throttle body and venturies, engine intake valves, etc.
Deposits adversely affect the operation of the vehicle. For example, deposits on the carburetor throttle body and venturies increase the fuel to air ratio of the gas mixture to the combustion chamber thereby increasing the amount of unburned hydrocarbon and carbon monoxide discharged from the chamber. The high fuel-air ratio also reduces the gas mileage obtainable from the vehicle.
Deposits on the engine intake valves when they get sufficiently heavy, on the other hand, restrict the gas mixture flow into the combustion chamber. This restriction, starves the engine of air and fuel and results in a loss of power. Deposits on the valves also increase the probability of valve failure due to burning and improper valve seating. In addition, these deposits may break off and enter the combustion chamber possibly resulting in mechanical damage to the piston, piston rings, engine head, etc.
The formation of these deposits can be inhibited as well as removed by incorporating an active detergent into the fuel. These detergents function to cleanse these deposit-prone areas of the harmful deposits, thereby enhancing engine performance and longevity. There are numerous detergent-type gasoline additives currently available which, to varying degrees, perform these functions.
A complicating factor has, however, recently arisen. With the advent of automobile engines that require the use of nonleaded gasolines (to prevent disablement of catalytic converters used to reduce emissions), it has been found difficult to provide gasoline of high enough octane to prevent knocking and the concomitant damage which it causes. The chief problem lies in the area of the degree of octane requirement increase, herein called "ORI", which is caused by deposits formed in the commercial gasoline.
The basis of the ORI problem is as follows: each engine, when new, requires a certain minimum octane fuel in order to operate satisfactorily without pinging and/or knocking. As the engine is operated on any gasoline, this minimum octane increases and, in most cases, if the engine is operated in the same fuel for a prolonged period, will reach an equilibrium. This is apparently caused by an amount of deposits in the combustion chamber. Equilibrium is typically reached after 5000 to 15,000 miles of automobile operation.
The octane requirement increase in particular engines used with commercial gasolines will vary at equilibrium from 5 or 6 octane units to as high as 12 or 15 units, depending upon the gasoline compositions, engine design and type of operation. The seriousness of the problem is thus apparent. A typical automobile with a research octane requirement of 85, when new, may after a few months of operation require 97 research octane gasoline for proper operation, and little unleaded gasoline of that octane is available. The ORI problem also exists in some degree with engines operated on leaded fuels. U.S. Pat. Nos. 3,144,311, 3,146,203 and 4,247,301 disclose lead-containing fuel compositions having reduced ORI properties.
The ORI problem is compounded by the fact that the most common method for increasing the octane rating of unleaded gasoline is to increase its aromatic content. This, however, eventually increases even more the necessary octane requirement. Moreover, some presently used nitrogen-containing compounds used as deposit-control additives and their mineral oil or polymer carriers may also significantly contribute to ORI in engines using unleaded fuels.
It is, therefore, particularly desirable to provide deposit control additives which effectively control the deposits in intake systems of engines, without themselves eventually contributing to the problem. The present invention discloses a new class of compounds which seek to do exactly that.
2. Prior Art
A prior class of deposit control additives generally including polyether amines includes U.S. Pat. No. 3,864,098 disclosing N-hydrocarby-N-heterocyclic polyamines displaying detergency in fuel concentration of 10-4,000 ppm. U.S. Pat. No. 4,247,301 teaches hydrocarbyl polyoxyalkylene polyamines as deposit control agents in fuels and dispersants in lubricating oils. U.S. Pat. No. 4,160,648 discloses deposit control additives, fuels containing them and lubricating oils having them as dispersant agents comprised of polyoxyalkylene carbamates.